Disassemblies are like source codes. You can modify them how you want, reassemble them, and play it. Even though the rom will be shifted, it will work because of labels. There are two types of disassemblies.
IDA are the ones for research. You can export an asm file from that as well.
Text are the ones that can be assembled in an assembler.
Split ones have all data split in categories and separate files, easier to modify. (you have to use Nemesis' tools to join them)